As a rule, a processing apparatus for photographic sheet material comprises several treatment cells, most of all of which are in the form of vessels containing a treatment liquid, such as a developer, a fixer or a rinse liquid. As used herein, the term "sheet material" includes not only photographic material in the form of cut sheets, but also in the form of a web unwound from a roll. The sheet material to be processed is transported along a sheet material path through these vessels in turn, by transport means such as one or more pairs of path-defining drive rollers, and thereafter optionally to a drying unit. The time spent by the sheet material in each vessel is determined by the transport speed and the dimensions of the vessel in the sheet feed path direction.
The apparatus may have a horizontal configuration, where a number of treatment cells are positioned one beside the other, or a vertical configuration where a number of treatment cells are positioned one above another in the form of a stack, with the sheet material moving either in an upwards, or in a downwards direction.
Since the path-defining rollers have an elastomeric surface, if the apparatus is left with the rollers biased together, even without any processing liquid being present, the rollers may become temporarily deformed. When the apparatus is re-started, this may result in poor quality image reproduction for the first few sheets processed from the re-start, after which the deformation disappears.
During the processing of the sheet material, the rollers may become coated with debris, such as gelatine from the sheet material. If the apparatus is switched off with the rollers stationary, some disturbing crystallisation on the rollers may occur, which may reduce the quality of the processed sheets. Moreover if the apparatus is left switched off with the rollers stationary and any roller pair biased together, then the rollers may become glued together by the gelatine.
Thus, from time to time it is necessary to clean the processing apparatus, in order to remove debris which may derive from the sheet material itself and deposits derived from the treatment liquids. The usual process for cleaning a processing apparatus, whether of the vertical or horizontal configuration, is to drain the treatment liquids and to flush the apparatus through with cleaning liquid. Water, optionally containing various additives and optionally at an elevation temperature, is the usual cleaning liquid.
A sheet material processing apparatus is knows, for example from EP 93201957.3 (Agfa-Gevaert NV) in which the path-defining rollers have a closed position in which they are biased into contact with each other to form a nip through which the sheet material path extends and an open position in which the path-defining rollers are spaced from each other. At each end of at least one of the rollers, displacement means are provided to move the rollers apart. To achieve this, the roller shafts are mounted in bearings held in slidably mounted sub-frames. The construction is however somewhat complicated.